Frazier emerged as the top contender in the late 1960s, defeating the likes of Jerry Quarry, Oscar Bonavena, Buster Mathis, Eddie Machen, Doug Jones, George Chuvalo and Jimmy Ellis en route to becoming undisputed heavyweight champion in 1970, and followed up by defeating Muhammad Ali on points in the highly-anticipated "Fight of the Century" in 1971. Two years later Frazier lost his title when he was knocked out by George Foreman. He fought on, beating Joe Bugner, losing a rematch to Ali, and beating Quarry and Ellis again.